Peter I. Pollak

The 1,2,5-Thiadiazoles

Publisher Summary This chapter presents the review of organic and physical chemistry of monocyclic 1, 2, 5-thiadiazoles up to the early part of 1967. Reference is made to the 2, 1, 3-benzothiadiazoles and related compounds only as they contribute to the chemistry of the basic ring system. The 1, 2, 5-thiadiazole nucleus is numbered as in 4. The hydrogenated forms are referred to as 1, 2, 5-thiadiazoline and 1, 2, 5-thiadiazolidine. The benzo derivatives are numbered and are named 2, 1, 3-benzothiadiazole, though much of the early literature makes use of the name piazthiole. The 1, 2, 5-thiadiazoles are very stable thermally. The unsubstituted ring is unchanged on heating at 220° and it has been reported that the potassium salt of 3-cyano-4-hydroxy-l, 2, 5-thiadiazoilse has table up to 360°. 1, 2, 5-thiadiazole generally resists electrophilic substitution. The compound is inert under various conditions of halogenation and nitration, and fails to enter the reactions with benzoyl chloride and aluminum chloride.